1. Field of the Invention
The invention relates to a robust method for estimating a rotation axis and a mass center of a spatial target based on binocular optical flows.
2. Description of the Related Art
It is one of the basic tasks for computer vision to calculate information of structure, position and motion of a target in a three-dimensional space according to two-dimensional image information obtained by cameras, and to reconstruct, identify and track the target thereby, where trajectory of each of the feature points on surface of the spatial target corresponds to a corresponding feature point in each image of an image sequence. Detection, identification and tracking of a spatial target followed by motion analysis and attitude estimation thereby are required for spatial tasks such as space rendezvous and docking of spacecrafts, fly-around and accompanying flying of a dual-satellite formation, and accompanying flying and navigation of a multi-satellite formation. Therefore, vision systems and algorithms featuring in high accuracy, external information independence, and excellent perception of complex environments are in urgent need to reconstruct attitude and trajectory of a spatial target, and highly accurate quantitative measurement should be performed on structure, trajectory, spatial position, and three-dimensional attitude of the target. Image sequence-based analysis is an important method for obtaining the information, however, reconstruction methods in prior art are limited in many ways for existence of areas ineffective for reconstructing three-dimensional motion vectors in an optical flow in a reconstruction process by binocular optical flows as a result of discretization errors, and it is critical to improve accuracy and stability of detection, tracking and reconstruction of a spatial target. There is provided a robust method for estimating a rotation axis and a mass center of a spatial target based on binocular optical flows, which is capable of improving accuracy of tracking and reconstruction of a trajectory of a spatial target effectively and reconstructing motion information of the spatial target accurately.
Motion structure reconstruction is a theory and a method for research in obtaining information of structure, position and motion of a target in a scenario from image sequences of the scenario, which is widely used in fields of robot navigation, automotive intelligent transportation, non-contact measurement of an object, etc. In unknown environments, autonomous navigation, such as robot navigation, space satellite tracking formation, etc., has technical difficulties not only in avoiding stationary objects, but also in adapting to a changing environment, and tracking, detecting and avoiding moving objects. On many occasions, a vision system is required to track and detect unknown objects automatically, and to realize close observation of properties and relative navigation of the unknown target, where it is critical to estimate a relative position and a relative attitude between a vision system and a target, and establish a motion equation of relative navigation. Therefore, mass center or a rotation axis of a target should be estimated first.
Errors may exist in reconstruction process in a conventional method for estimating a rotation axis and a mass center of a spatial target based on binocular optical flows, which does not analyze reasons for the errors and does not provide a corresponding solution. However, the present invention analyzes the existing problems and provides a solution.